linux-kernel - Re: [PATCH 4.19 72/98] x86/CPU/AMD: Clear RDRAND CPUID bit on AMD family 15h/16h

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Message-ID: <20190828114947.GC8052@amd>
Date:   Wed, 28 Aug 2019 13:49:47 +0200
From:   Pavel Machek <pavel@...x.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Pavel Machek <pavel@...x.de>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-kernel@...r.kernel.org, stable@...r.kernel.org,
        Tom Lendacky <thomas.lendacky@....com>,
        Borislav Petkov <bp@...e.de>,
        Andrew Cooper <andrew.cooper3@...rix.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Chen Yu <yu.c.chen@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        Jonathan Corbet <corbet@....net>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Juergen Gross <jgross@...e.com>,
        Kees Cook <keescook@...omium.org>,
        "linux-doc@...r.kernel.org" <linux-doc@...r.kernel.org>,
        "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        "x86@...nel.org" <x86@...nel.org>
Subject: Re: [PATCH 4.19 72/98] x86/CPU/AMD: Clear RDRAND CPUID bit on AMD
 family 15h/16h

Hi!

> > > There is no way to reinitialize RDRAND from the kernel otherwise we would
> > > have exactly done that. If you know how to do that please tell.
> > 
> > Would they? AMD is not exactly doing good job with communication
> 
> Yes they would. Stop making up weird conspiracy theories.

> > here. If BIOS can do it, kernel can do it, too...
> 
> May I recommend to read up on SMM and BIOS being able to lock down access
> to certain facilities?
> 
> > or do you have information saying otherwise?
> 
> Yes. It was clearly stated by Tom that it can only be done in the
> BIOS.

Do you have a link for that? Because I don't think I seen that one.

> > > Also disabling it for every BIOS is the only way which can be done because
> > > there is no way to know whether the BIOS is fixed or not at cold boot
> > > time. And it has to be known there because applications cache the
> > 
> > I'm pretty sure DMI-based whitelist would help here. It should be
> > reasonably to fill it with the common machines at least.
> 
> Send patches to that effect.

Why should it be my job? AMD screwed this up, they should fix it
properly. And you should insist on proper fix.

> > Plus, where is the CVE, and does AMD do anything to make BIOS vendors
> > fix them?
> 
> May I redirect you to: https://www.amd.com/en/corporate/contact

That will certainly make communication easier, right.

								Pavel
-- 
DENX Software Engineering GmbH,      Managing Director: Wolfgang Denk
HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany

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